That's when David's grandfather remembered a man he met six weeks earlier who needed a heart transplant. David's young heart was a perfect match for the father of two.

A file photo of heart transplant recipient Rodney DuBaun and his children after receiving the organ donated by David Nicklas Jr. in 1993.

"I can never repay what I've got," DuBaun said.

What DuBaun got was the chance to see his own family grow together with David's.

"I consider Rodney a son," Nicklas said.

"They're like they've been my family my whole life," DuBaun added.

Heart transplant recipient Rodney DuBaun, center, and David Nicklas Sr., left, whose son donated the heart, at the Texas Rangers game on April 19, 2016.

And now they work together as The Nicklas Foundation, promoting organ donation. They raised awareness Tuesday evening by presenting the game ball at the Rangers game in David's memory. They want those watching to remember that even heartbreaking endings can create new joy.

"You don't know who you're going to help," said DuBaun. "And that's the most important thing!"